(from impluere, to rain into) is the sunken section in the centre of the atrium in Roman dwellings. It worked as a cistern or a tank to collect the water from the compluvium of the roof. It is usually made of marble and placed about 30 cm below the floor of the atrium. Water pours both from the gutter, through the rain pipes and is then collected in the basin in the impluvium in the middle of the atrium.